[PATCH 2/3] platform/x86: dell-laptop: Don't use an unread keyboard state at init

[Rosen Penev <rosenp@gmail.com>]

kbd_init_info() ignores the return value of kbd_get_state(). If the
call fails, the uninitialized state on the stack is used to set
kbd_previous_level and kbd_previous_mode_bit, which are later sent to
the BIOS when triggers are enabled or the backlight is turned back on.

Return the error instead. kbd_get_info() has already filled in
kbd_info at that point, so clear it as well: level control through
kbd_get_state() cannot work, and kbd_init() then still registers the
LED if at least two keyboard backlight tokens are available, which
works without it.

Fixes: 02b2aaaa57ab ("platform: x86: dell-laptop: Add support for keyboard backlight")
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/platform/x86/dell/dell-laptop.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/dell/dell-laptop.c b/drivers/platform/x86/dell/dell-laptop.c
index bee347e1d60c..171728d63c81 100644
--- a/drivers/platform/x86/dell/dell-laptop.c
+++ b/drivers/platform/x86/dell/dell-laptop.c
@@ -1455,7 +1455,12 @@ static inline int kbd_init_info(void)
 	    dell_smbios_find_token(KBD_LED_AC_TOKEN))
 		kbd_timeout_ac_supported = true;
 
-	kbd_get_state(&state);
+	ret = kbd_get_state(&state);
+	if (ret) {
+		/* Leave level control to the SMBIOS tokens, if there are any */
+		memset(&kbd_info, 0, sizeof(kbd_info));
+		return ret;
+	}
 
 	/* NOTE: timeout value is stored in 6 bits so max value is 63 */
 	if (kbd_info.seconds > 63)
-- 
2.56.0